Refining element

ABSTRACT

Refining elements for use with disc refiners for the processing of fibrous materials are disclosed. The refining element include a refining surface having a plurality of bars and intermediate grooves, with the bars having an upper surface and a pair of side surfaces defining longitudinal edges, with the plurality of bars including a plurality of recesses disposed along at least one of the longitudinal edges, the recesses including open portions in both the upper surface and one of the side surfaces thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national phase entry under 35 U.S.C. §371of International Application No. PCT/SE04/000678 filed May 5, 2004,published in English, which claims priority from Swedish PatentApplication No. 0301525-2 filed May 23, 2003, all of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to refiners of the disc-type, with opposedrefining discs rotating relative to one another. The refining discs areprovided with refining elements, which between themselves form arefining gap with a refining zone for working fibrous material. Thefibrous material preferably is lignocellulosic fibrous material and therefiner is used for the manufacture of, for example, reject pulp,recycled fiber pulp and mechanical pulps, such as board pulp,thermomechanical pulp (TMP) and chemi-thermo-mechanical pulp (CTMP) andfor low-concentration refining chemical pulps.

The present invention, more precisely, relates to a refining element foruse in a refiner of the above kind.

BACKGROUND OF THE INVENTION

A refining element is generally formed with a pattern of bars andintermediate grooves. The bars and grooves are formed in different ways,depending on which fibrous material is worked and the degree of refiningdesired and, thus, in the case of lignocellulosic material, the pulpquality which is desired. The bars have an upper surface and sidesurfaces so that longitudinal edges are formed between the upper surfaceand respective side surface. The bars can be, for example, continuous ordiscontinuous, and can be arranged in different patterns. The working ofthe fibrous material is substantially carried out by the bars of therefining elements. The refining gap is formed so that the fibrousmaterial, seen in the radial direction, passes from the insideoutwardly. Farthermost inward in the refining gap the refining elementsare normally formed so as to bring about a first disintegration of thematerial and to advance the material outwardly in the refining gap. Acertain defibering, i.e. separation of the fibers of the lignocellulosicmaterial, also takes place in the inner portion of the refining gapwhere the distance between the refining surfaces is the greatest.Thereafter, that distance decreases outwardly in order that the desiredworking or refining of the fibrous material shall be obtained.

During the refining of fibrous material of high concentration, and aboveall at high energy inputs, it has been found necessary to place flowrestrictions, so-called dams, in the grooves of the refining elements inorder to prevent unworked material from passing out through the refininggap. These dams, however, form an obstacle for the steam developing inthe refining gap during the refining. A high steam pressure is therebycreated in the refining gap. This high steam pressure has a negativeeffect on the capacity and operational stability of the refiner. It alsoimplies a limitation on the possible energy input. The developed steam,thus, will be forced by the flow restrictions upwardly out of thegrooves, and will disturb the material flow through the refining gap.

One way of solving this problem would be to supply dilution water to therefining gap in order to thereby condense the steam. This, however,results in reducing the material concentration to a low level, and thusin a deteriorated pulp quality.

During the working or refining of fibrous material with lowconcentration no steam development takes place, and the material ispartially transported by the liquid flow out of the refining gap. Alsoin this case dams are usually used to prevent unworked material frompassing out through the refining gap. It can imply, however, that theflow through the refining gap will be much too low.

SUMMARY OF THE INVENTION

In accordance with the present invention, these and other objectiveshave now been realized by the discovery of a refining element for usewith disc refiners for the processing of fibrous materials, the refiningelement comprising a refining surface including a plurality of bars andintermediate grooves therebetween, the plurality of bars including anupper surface and a pair of side surfaces defining longitudinal edgestherebetween, the plurality of bars including a plurality of recessesdisposed along at least one of the longitudinal edges, the plurality ofrecesses including open portions in both the upper surface and one ofthe side surfaces thereof. In a preferred embodiment, the plurality ofrecesses are disposed along only one of the longitudinal edges. Inanother embodiment, the plurality of recesses are disposed along both ofthe longitudinal edges.

In accordance with one embodiment of the refining element of the presentinvention, the upper surface includes a predetermined central pointsubstantially at the center of the upper surface of the plurality ofbars, and wherein the plurality of recesses extend inwardly from the oneof the side surfaces to the predetermined central point.

In accordance with another embodiment of the refining element of thepresent invention, the plurality of recesses have a depth of from 2 to 5mm as measured from the longitudinal edge.

In accordance with another embodiment of the refining element of thepresent invention, the plurality of recesses have a width of from 2 to 5mm.

In accordance with another embodiment of the refining element of thepresent invention, the plurality of recesses are spaced apart a distanceof from 1 to 10 mm.

In accordance with another embodiment of the refining element of thepresent invention, the plurality of recesses form an angle of from 45°to 90° with respect to the plurality of bars, as measured in theintended direction of flow of the fibrous material along the refiningsurface. Preferably, the plurality of recesses are disposedsubstantially across the plurality of bars.

The present invention offers a solution to the above problems. Accordingto the present invention, the bars are provided with a plurality ofrecesses, which are arranged in the longitudinal edges of the bars. Therecesses are directed across the bars or so as to form an angle of atleast 45° with the bars. The recesses are open both to the upper surfaceof the bars and to one side surface or to both side surfaces. By thisconfiguration of the bars the flow of the fibrous material through therefining gap will be braked, so that the stay-time of the fibers in therefining gap will be longer and the working thereby will be increased,without braking the steam or liquid flow in the grooves between the barsso that the flow of the fibrous material is disturbed.

The recesses can be placed, for example, along the entire length of thebars or can be broken off by small portions without recesses, measuredin the longitudinal direction of the bars. Each recess can have aconstant or a varying depth along the bars in the upper surface and sidesurfaces of the bars. The recesses can be formed only on one side or onboth sides of the bars.

When the recesses are formed only on one side of the bars, the directionof rotation of the refining discs carrying the refining elements cannotbe changed. Such a configuration, however, can still be suitable with aview to strength.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail in the followingdetailed description which, in turn, refers to the accompanying Figuresillustrating some embodiments of the present invention, as follows:

FIG. 1 is a top, elevational, front side view of a refining segment witha pattern of bars and intermediate grooves;

FIG. 2 is an enlarged, top, elevational view of the upper surface of thebars used in the present invention;

FIG. 3 is an enlarged, top, elevational view of the upper surface of thebars of another embodiment of the present invention;

FIG. 4 is a side, elevational, cross-sectional view of one alternativeof the embodiment shown in FIG. 2; and

FIG. 5 is a side, elevational, cross-sectional view of anotheralternative of the embodiment shown in FIG. 2.

DETAILED DESCRIPTION

FIG. 1 shows a refining element 10 intended for refining fibrousmaterial having a high concentration. The refining element 10 isprovided with a pattern of bars 11 and intermediate grooves 12, in whichthe bars have upper surfaces 13 and side surfaces 14 with edges 15. Thepattern is divided into two zones, an inner zone 16 and an outer zone17, where the bars and grooves in the inner zone are coarser than in theouter zone. The bars in the inner zone are intended to bring about afirst disintegration of the material and to advance the materialoutwardly to the outer zone. The bars in the outer zone are more tightlyarranged, which yields more bar edges for effecting the substantialworking and refining of the fibrous material. The pattern can alsocomprise more zones, where the pattern is usually made tighter from zoneto zone, as seen radially outwardly.

FIG. 2 shows one embodiment of a bar 11 on a refining element accordingto the present invention. Along the bar 11 a plurality of recesses 18are placed. The recesses are arranged slightly angularly in relation tothe longitudinal direction of the bars and are open both to the uppersurface 13 and the side surface 14. The recesses can suitably extend toabout the center of the upper surface of the bar. The depth of therecesses, as measured from the edge, are one or some millimeters,preferably 2-5 mm. The width should also be one or more millimeters,preferably 2-5 mm. Bars thereby have toothed edges. The distance betweenadjacent recesses should be 1-10 mm, preferably 2-5 mm.

FIG. 3 shows another embodiment of a bar 11. As compared to FIG. 2, inthis case the recesses 18 are located at both edges 15 of the bar, sothat both edges of the bar are toothed. As regards the configuration ofthe recesses, the same dimensions apply as in the case of the FIG. 2embodiment. In this case, the recesses on opposed edges 15 are suitablyoffset, so that they do not lie directly in front of each other. Thisimplies that a refining element with such bars can rotate in bothdirections.

The form of the bottom of the recesses 18 can be rectilinear, as shownin FIG. 4, or curved, as shown in FIG. 5. Other forms can also beimagined. The recesses are arranged across the bars or form an angle ofat least 45° with respect to the longitudinal direction of the bars.This applies primarily to the surface, which outwardly defines a recess18, as measured in the direction of flow of the material. When therecesses 18 are angular, they extend from the side surfaces 14 obliquelyoutwardly, as measured in the direction of flow of the material.

Bars with a configuration according to the present invention can beplaced on any zone on the refining element, but preferably in an outerzone where the working and refining are most intensive and the distancebetween opposed refining elements is the shortest, i.e. where therefining gap is the smallest and the steam development the greatest.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1-9. (canceled)
 10. A refining element for use with disc refiners forthe processing of fibrous materials, said refining element comprising arefining surface including a plurality of bars and intermediate groovestherebetween, said plurality of bars including an upper surface and apair of side surfaces defining longitudinal edges therebetween, saidplurality of bars including a plurality of recesses disposed along atleast one of said longitudinal edges, said plurality of recessesincluding open portions in both said upper surface and one of said sidesurfaces thereof.
 11. The refining element of claim 10 wherein saidplurality of recesses are disposed along only one of said longitudinaledges.
 12. The refining element of claim 10 wherein said plurality ofrecesses are disposed along both of said longitudinal edges.
 13. Therefining element of claim 10 wherein said upper surface includes apredetermined central point substantially at the center of said uppersurface of said plurality of bars, and wherein said plurality ofrecesses extend inwardly from said one of said side surfaces to saidpredetermined central point.
 14. The refining element of claim 10wherein said plurality of recesses have a depth of from 2 to 5 mm asmeasured from said longitudinal edge.
 15. The refining element of claim10 wherein said plurality of recesses have a width of from 2 to 5 mm.16. The refining element of claim 10 wherein said plurality of recessesare spaced apart a distance of from 1 to 10 mm.
 17. The refining elementof claim 10 wherein said plurality of recesses form an angle of from 45°to 90° with respect to said plurality of bars, as measured in theintended direction of flow of said fibrous material along said refiningsurface.
 18. The refining element of claim 14 wherein said plurality ofrecesses are disposed substantially across said plurality of bars.